1. Field of the Invention
This invention relates to cameras, and more particularly to a device which can be used in or with a camera for the purpose of reducing the incidence of eye closures of an intended subject when the subject is being photographed.
2. Description of the Prior Art
Recent studies indicate that about one of every twenty photographs (5%) taken of a single human subject is unsatisfactory because the eyes of the subject being photographed were closed at the time the picture was taken. If a group of people are photographed, the number of unsatisfactory pictures increases in proportion to the number of persons in the group.
A voluntary blink cannot be distinguished objectively from one that is involuntary. For the most part, a blink is an unconscious, involuntary, periodic reflex movement. It is this involuntary blink response with which this invention is concerned.
For most individuals, provided that the conditions remain constant, the average value of the interval between successive blinks (inter-blink period) is remarkably constant. Blinking movements occur at intervals of from 2 to 10 seconds, with the average person blinking at a rate of approximately 12.5 blinks/min. with the blink lasting about 0.2-0.3 sec. This data suggest that vision is interrrupted about every 5 sec. with a 0.25 sec. blackout, which means that the average person is without vision 5-6% of his or her wakeful hours. The minimum interblink period (also called refractory period) for involuntary blinks induced by bright flashes of light is about 0.5 sec. or perhaps slightly longer. Each individual appears to have a definite rhythm, in which blinks occurring after short inter-blink periods (1 to 2 seconds) may sometimes be followed by a series of blinks having longer inter-blink periods (on the order of say 10 seconds); but for the same individual, the distribution of movements is very constant, provided the conditions remain constant. If an attempt is made to stop the movements voluntarily, an almost irresistible impulse to blink asserts itself within a short time. On the other hand, once the blink action starts, whether voluntarily or involuntarily, it completes its action without interruption.
This phenomenon of blinking has unexpected repercussions in many phases of human activity. One important consequence is in the art of photography, where the foregoing information shows that in a group of people having normal blinking behavior, a definite percentage (approximately 5%) of them will at any moment be in the act of blinking. This prediction is confirmed by the examination of group photographs. Thus, in any photograph of 40 people, one can usually expect to find 2 or 3 people with their eyes closed in the act of blinking; likewise with 20 people in the photograph, 1 or 2 would appear to have their eyes closed. A truly satisfactory solution to this problem has not yet been achieved.